1. Field of the Invention
The present invention relates to an information processing system, an information processing apparatus and method, recording medium, and program, and more particularly, to an information processing system, an information processing apparatus and method, recording medium, and program which are useful to construct a network.
2. Description of Related Art
With the recent advance of network facilities, there has been proposed an idea that domestic electric appliances should also be organized into a network. Networked electric appliances would permit centralized control and data exchange among them. Moreover, it would be possible to control electric appliances from outside through a communication line connected to the domestic network.
Networking domestic electric appliances with wires is troublesome and poor in appearance. In order to solve this problem, there has been proposed an idea of using the power line to supply electric appliances with power as well as data.
The advantage of this idea is that the commercial power line (100V, 50 or 60 Hz) can transmit from outside spectrum spread modulation signals or OFDM (Orthogonal Frequency Division Mutliplex) modulation signals without affecting them.
The problem with networking with power lines is that signals with frequencies other than 50 or 60 Hz result in very low impedances, say, 1 ohm or lower (depending on the power-factor capacitor or power-supply filter) or LC oscillation with the inductance of the transformer because the power line is so designed as to transmit electric power most effectively at a frequency of 50 or 60 Hz.
In addition, the impedance becomes very high (say, 100 ohms or higher) in the absence of load. Because there is the possibility of impedance fluctuating considerably, stable communications need a dynamic range of 90 dB, a drive circuit which operates efficiently over a broad range of impedance, and a large power amplifier.
Change in impedance leads to change in load current flowing from electric appliances. The conventional way to cope with this situation is by correction which is accomplished as follows. First, ac load current is previously measured in the non-modulation period. Then, modulation signals (or signals carrying data) are sent. The present load current is estimated from the previously measured load current. The estimated load current is subtracted to make correction. The disadvantage of this method is that adequate estimate is impossible in the case where load current rapidly changes and hence the calculated load current may be erroneous.
The present invention was completed in view of the foregoing. It is an object of the present invention to provide a simple, safe domestic network for electric appliances in which data is sent by modulating the voltage or current signals of power supply and corrections are made in response to electric appliances varying in load.
The first aspect of the present invention is directed to an information processing system of the type having a first information processing apparatus to send data, a second information processing apparatus to receive and process said data, and a third information processing apparatus connected to said first information processing apparatus, wherein said first information processing apparatus contains a means to modulate current in response to data to be transmitted and a means to supply a first current which has been modulated by said modulating means to said second information processing apparatus; said second information processing apparatus contains a means to input a third current which has been synthesized from said first current supplied from said supply means and a second current output from said third information processing apparatus, a means to estimate said second current, a means to extract said first current by subtracting said second current (which has been estimated by said estimating means) from said third current which has been entered from said input means, and a means to demodulate said data from said first current extracted by said extracting means; and said third information processing apparatus contains a means to execute processing in response to instructions from said first information processing apparatus.
The second aspect of the present invention is directed to an information processing apparatus which comprises a means to input a third current which has been synthesized from a first current modulated in response to data and a second current output from another unit, a means to estimate said second current, a means to extract said first current by subtracting said second current (which has been estimated by said estimating means) from said third current which has been entered from said input means, and a means to demodulate said data from said first current extracted by said extracting means.
According to the third aspect, the information processing apparatus according to the second aspect is modified such that said estimating means samples the third current at a multiple of the frequencies of the power voltage applied to other apparatus and integrates the sampled values, thereby estimating the second current.
According to the fourth aspect, the information processing apparatus according to the third aspect is modified such that said estimating means performs sampling within a sampling time which is 50 times the frequency and processes the 50 sampled values in parallel.
According to the fifth aspect, the information processing apparatus according to the second aspect is modified such that said demodulating means judges the sign of the first current, thereby demodulating data.
The sixth aspect of the present invention is directed to an information processing method which comprises a step of controlling input of a third current which has been synthesized from a first current modulated in response to data and a second current output from other apparatus, a step of estimating said second current, a step of extracting said first current by subtracting said second current estimated in said estimating step from said third current whose input is controlled by processing in said input control step, and a step of demodulating said data from said first current extracted in said extracting step.
The seventh aspect of the present invention is directed to a recording medium storing a program that can be read by a computer, said program comprising a step of controlling input of a third current which has been synthesized from a first current modulated in response to data and a second current output from other apparatus, a step of estimating said second current, a step of extracting said first current by subtracting said second current estimated in said estimating step from said third current whose input is controlled by processing in said input control step, and a step of demodulating said data from said first current extracted in said extracting step.
The eighth aspect of the present invention is directed to a program to be executed by a computer, said program comprising a step of controlling input of a third current which has been synthesized from a first current modulated in response to data and a second current output from other apparatus, a step of estimating said second current, a step of extracting said first current by subtracting said second current estimated in said estimating step from said third current whose input is controlled by processing in said input control step, and a step of demodulating said data from said first current extracted in said extracting step.
In the information processing system according to the present invention, the first information processing apparatus modulates current in response to data to be transmitted and supplies the modulated first current to the second information processing apparatus, the second information processing apparatus inputs the third current which has been synthesized from the first current and the second current output from the third information processing apparatus, estimates the second current, extracts the first current by subtracting the estimated second current from the third current entered, and demodulates the data from the extracted first current, and the third information processing apparatus executes processing in response to instructions from the first information processing apparatus.
The information processing apparatus and method, and program according to the present invention are so designed as to enter the third current which has been synthesized from the first current modulated in response to data and the second current output from other apparatus is entered, estimate the second current, subtract the second current from the third current, extract the first current, and demodulate data from the extracted first current.